In an image forming apparatus such as a laser printer, an electrostatic latent image is formed on a surface of a photosensitive drum, and toner is supplied to the electrostatic latent image from a developer cartridge, whereby a toner image is carried on the surface of the photosensitive drum. Then, the toner image is transferred onto a sheet. Thus, an image is formed on the sheet.
The developer cartridge includes a casing which contains toner and has an opening facing toward the photosensitive drum. The developer cartridge further includes a developing roller rotatably provided in the casing as being exposed from the opening of the casing, a layer-thickness regulating blade provided in the casing for regulating the thickness of a toner layer carried on the developing roller, and seal members provided in the casing for preventing the toner from leaking from axially opposite end portions of the developing roller.
Referring to FIG. 11, a developer cartridge 151 is illustrated as such a developer cartridge.
In FIG. 11, the developer cartridge 151 includes a casing 152 having an opening 153 extending longitudinally thereof, and a layer-thickness regulating blade 154 provided in the opening 153 of the casing 152 as extending longitudinally of the opening 153.
The layer-thickness regulating blade 154 includes a blade 155 and a pressure contact rubber 156. The blade 155 is of a thin plate shape, and has a fixed downstream edge portion (an upper edge portion in FIG. 11) on a downstream side with respect to the direction of the rotation of the developing roller 160 (see FIG. 12). The pressure contact rubber 156 is provided on a free upstream edge portion (a lower edge portion in FIG. 11) of the blade 155 on an upstream side with respect to the rotation direction of the developing roller 160 as extending to the vicinities of longitudinally opposite end portions of the blade 155.
Further, seal members 157 are respectively provided on longitudinally opposite end portions of the opening 153. The seal members 157 are disposed along the rotation direction of the developing roller 160. Downstream end portions 158 of the seal members 157 located downstream with respect to the rotation direction of the developing roller 160 are respectively attached to surfaces of the longitudinally opposite end portions of the blade 155 in adjoining relation to longitudinally opposite ends of the pressure contact rubber 156. Further, upstream end portions 159 of the seal members 157 located upstream with respect to the rotation direction of the developing roller 160 are respectively attached to surfaces of end portions of the casing 152.
In the developer cartridge shown in FIG. 11, therefore, the developing roller 160 is kept in pressure contact with surfaces of the aforementioned seal members 157 as shown in FIG. 12. When the developing roller 160 is rotated in an arrow direction in a developing process, the toner is disadvantageously liable to leak through boundary portions 161 between the seal members 157 and the pressure contact rubber 156 in the rotation direction of the developing roller 160 as shown in FIG. 11.